Zilog Z80 Instruction Set: Difference between revisions
Updated single-byte instructions chart. Not done yet. |
m Added link to NOP. |
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! 7 || 6 || 5 || 4 || 3 || 2 || 1 || 0 || b2 || b3 | ! 7 || 6 || 5 || 4 || 3 || 2 || 1 || 0 || b2 || b3 | ||
|- | |- | ||
| 0 || 0 || 0 || 0 || 0 || 0 || 0 || 0 || — || — ||align="left"| NOP ||align="left"| No operation | | 0 || 0 || 0 || 0 || 0 || 0 || 0 || 0 || — || — ||align="left"| [[Zilog Z80 Instruction Set#NOP|NOP]]|| align="left" | No operation | ||
|- | |- | ||
| 0 || 0 ||colspan="2"| rr || 0 || 0 || 0 || 1 || n-lo || n-hi ||align="left"| LD rr, nn ||align="left"| rr ← nn | | 0 || 0 ||colspan="2"| rr || 0 || 0 || 0 || 1 || n-lo || n-hi ||align="left"| LD rr, nn ||align="left"| rr ← nn | ||
Revision as of 04:50, 2 June 2026
Instructions by Opcode
| Mnemonic | Description |
|---|---|
| b | Identifies a one-bit expression in the range (0 to 7). The most-significant bit to the left is bit 7 and the least-significant bit to the right is bit 0. |
| cc | Identifies the status of the Flag Register as any of (NZ, Z, NC, C, PO, PE, P, or M) for the conditional jumps, calls, and return instructions. |
| d | Identifies a one-byte signed integer expression in the range ( -128 to +127). |
| e | Identifies a one-byte signed integer expression in the range (-126 to +129) for relative jump offset from current location. |
| m | Identifies any one of r, (HL), (IX+d) or (IY+d). |
| n | Identifies a one-byte unsigned integer expression in the range (0 to 255). |
| nn | Identifies a two-byte unsigned integer expression in the range (0 to 65535). |
| pp | Identifies any one of the 16-bit registers BC, DE, IX, SP. |
| Identifies any one of the 16-bit registers BC, DE, HL, AF. | |
| r | Identifies any one of the 8-bit registers A, B, C, D, E, H, L. |
| rr | Identifies any one of the 16-bit registers BC, DE, IY, SP. |
| ss | Identifies any one of the 16-bit registers BC, DE, HL, SP. |
| (HL) | Identifies the contents of the memory location, whose address is specified by the contents of the register pair HL. |
| (IX+d) | Identifies the contents of the memory location, whose address is specified by the contents of the IX Index Register plus the signed displacement d. |
| (IY+d) | Identifies the contents of the memory location, whose address is specified by the contents of the IY Index Register plus the signed displacement d. |
Single-byte Instructions
| Opcode | Operands | Mnemonic | Description | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | b2 | b3 | ||
| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | — | — | NOP | No operation |
| 0 | 0 | rr | 0 | 0 | 0 | 1 | n-lo | n-hi | LD rr, nn | rr ← nn | |
| 0 | 0 | rr | 0 | 0 | 1 | 0 | — | — | LD (rr), A | rr ← A | |
| 0 | 0 | ss | 0 | 0 | 1 | 1 | — | — | INC ss | ss ← ss + 1 | |
| 0 | 0 | r | 1 | 0 | 0 | — | — | INC r | r ← r + 1 | ||
| 0 | 0 | r | 1 | 0 | 1 | — | — | DEC r | r ← r - 1 | ||
| 0 | 0 | r | 1 | 1 | 0 | n | — | LD r, n | r ← n | ||
| 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | — | — | RLCA | A1-7 ← A0-6; A0 ← Cy ← A7 |
| 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | — | — | EX AF,AF' | AF ↔ AF |
| 0 | 0 | rr | 1 | 0 | 0 | 1 | — | — | ADD HL, rr | HL ← HL + rr | |
| 0 | 0 | rr | 1 | 0 | 1 | 0 | — | — | LD A, (rr) | A ← (rr) [BC or DE only] | |
| 0 | 0 | rr | 1 | 0 | 1 | 1 | — | — | DEC rr | rr ← rr - 1 | |
| 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | — | — | RRCA | A0-6 ← A1-7; A7 ← Cy ← A0 |
| 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | d | — | DJNZ d | B = B - 1; if B ≠ 0 then PC ← PC + d |
| 0 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | — | — | RLA | A1-7 ← A0-6; Cy ← A7; A0 ← Cy |
| 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | d | — | JR d | PC ← PC + d |
| 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | — | — | RRA | A0-6 ← A1-7; Cy ← A0; A7 ← Cy |
| 0 | 0 | 1 | cc | 0 | 0 | 0 | d | — | JR cc, d | If cc0-1 true, PC ← PC + d (Only 2 bits of cc used: NZ, Z, NC, C) | |
| 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | n-lo | n-hi | LD (nn), HL | (nn) ← HL |
| 0 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | — | — | DAA | @ |
| 0 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | n-lo | n-hi | LD HL, (nn) | HL ← (nn) |
| 0 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | — | — | CPL | A ← ¬A |
Instructions by Group
8-bit Load Group
16-bit Load Group
Exchange, Block Transfer, Search Group
General Purpose Arithmetic and CPU Control Group
NOP
Operation
—
Op Code
NOP
| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 00 |
Operands
None.
Description
The CPU performs no operation during the machine cycle.
| M-Cyles | T-States | 4 MHz E.T. |
|---|---|---|
| 1 | 4 | 1.0 |
Condition Bits Affected
None.